This invention relates to spring-driven tap changers, and more particularly, to a protective means for the driving gear and boss of such spring-driven changer.
As is well known to those skilled in the tap changer art, many tap changer mechanisms utilize a spring drive to provide a rapid, snap-opening of contacts to prevent arcing damage to such contacts. One such mechanism is shown in U.S. Pat. No. 2,878,333 issued in the names of O. P. McCarty and J. R. Barr and assigned to the same assignee as this invention. One problem with such mechanism is the possibility of breakage of either the driving boss or the driving gear when the tap changer signal is removed before the spring begins the tap change, but after it has been cranked, or loaded, near to the dead center position. In that position, the drive gear could reverse and the spring suddenly be released. If this should occur, the crank could strike the boss, breaking it or the drive gear on which it is mounted.
It has been discovered that a protective means to prevent such damage may be provided to the driving gear and boss of the spring-actuated tap changer. In one embodiment, the protective means may take the form of a pair of hook cams which are pivotally mounted on the crank, the hook cams engaging the boss should the boss attempt reverse rotation, prior to the actuation of the tap change. The protective means prevent the release of the crank into sudden engagement with the boss, which could damage either the boss or the driving gear.
It is, therefore, a principal object of this invention to provide a protective means for the driving gear and boss of a spring-driven tap changer.
A further object of this invention is to provide a hook device on the crank of a spring-driven tap changer to engage the driving boss in a reverse rotation to prevent release of the crank in a manner as would strike the boss to cause damage thereto.